This invention relates generally to alkoxylated acrylate and methacrylate macromonomers useful for preparing water-reducing additives for concrete, ultraviolet light (UV)-cured adhesives, and water-dispersed polyurethanes. The macromonomers are prepared using the continuous addition of starter in order to minimize the by-product formation during the alkoxylation reaction used to produce the macromonomer.
Polyols produced using a double metal cyanide (DMC) catalyst are known to possess advantageous properties, such as low ethylenic unsaturation. Particularly preferred polyols made using these DMC catalysts are produced using a continuous addition of starter, together with optional initially charged starter, during the polymerization of epoxide to produce the desired polyol, as described in more detail in U.S. Pat. No. 5,777,177. The ""177 patent teaches the use of water or a low molecular weight polyol as the starter, and discloses that the resulting polyol has a reduced amount of high molecular weight tail.
The continuous addition of other starters, such as hydroxypropylmethacrylate (HPMA) to initiate the polymerization of an epoxide, such as propylene oxide or ethylene oxide, in the presence of a DMC catalyst, is described in U.S. Pat. No. 5,854,386, notably at column 3, lines 13-16, and column 6, lines 15-18 thereof. The ""386 patent discloses that this methodology is useful in preparing stabilizers for polymer polyols and impact modifiers made by reacting the stabilizer with one or more polymerizable vinyl monomers. This process is described in more detail in the paragraph bridging columns 7 and 8 of that patent. The ""386 patent is incorporated herein by reference in its entirety.
Due to the hydrophobic nature of many polyurethanes, there is a need to employ a dispersion stabilizer when preparing water-dispersed polyurethanes in order to prevent the dispersion from xe2x80x9cbreakingxe2x80x9d by virtue of precipitation or agglomeration of the polyurethane component. Conventional dispersion stabilizers for water-dispersed polyurethanes are typically expensive, and oftentimes do not perform as well as might be desired. For example, 2,2-dimethyol propionic acid (DMPA) is costly, in short supply, and typically does not provide acid groups in the desired location on the urethane molecule, namely in the middle of the hydrophobic polyether portion of the molecule, upon reaction with an isocyanate.
There currently is a need in the polyurethanes manufacturing community for inexpensive, homogeneous macromonomer compositions that are useful in preparing water-dispersed polyurethanes having alcohol water-dispersing moieties in a middle portion of the urethane molecules. The present invention provides one solution to this need by using xe2x80x9ccontinuous addition of starterxe2x80x9d (CAOS) methodology to prepare alkoxylated macromonomers, such as propoxylated acrylate- and propoxylated methacrylate- macromonomers. These macromonomers can be copolymerized with an acid, or combination of acids, to produce a stabilizer for water-dispersible polyurethanes. Alternatively, these macromonomers can be co-polymerized with a monomer, or combination of monomers, to produce copolymers that are useful as additives in concrete-forming compositions. These additives permit the use of a reduced amount of water in fabricating the concrete, and provide a further improvement over the water-reducing agents described in co-pending U.S. application Ser. No. 09/358,009 filed Jul. 21, 1999. These copolymers are also useful as additives in UV-curable adhesives in order to enhance the adhesive""s performance.
One aspect of this invention provides an improved process for producing an alkoxylated acrylate macromonomer or an alkoxylated methacrylate macromonomer. The alkoxy moiety of the macromonomer contains between one and six carbons. In the process, a first component, namely a hydroxyalkylacrylate or a hydroxyalkylmethacrylate, is reacted with a second component, namely an alkylene oxide compound (preferably an alkylene oxide selected from the group consisting of ethylene oxide, propylene oxide, butylene oxide, and combinations thereof). The macromonomer is produced by co-feeding the reactants into the reaction vessel co-currently or counter-currently, and carrying out the reaction at a reaction temperature of between about 60xc2x0 C. and about 130xc2x0 C. in the presence of a DMC catalyst, and optionally in the presence of a solvent. The reaction employs a CAOS method whereby the first component is added to a reactor already containing at least some amount of the second component. Use of this CAOS method facilitates production of the desired macromonomer, and reduces the likelihood of forming unwanted byproducts.
In another aspect, the present invention comprises co-polymerizing the above-described macromonomer with a monomer selected from the group consisting of acrylic acid, methacrylic acid, fumaric acid, styrene, maleic acid, methyl methacrylate, and combinations thereof. The resulting copolymer is useful as a water-reducing additive for concrete formation. When this water-reducing additive is present in a reaction mixture comprising sand, cement, and water, less water is needed than the amount that is necessary to prepare concrete in the absence of the water-reducing additive.
In still another aspect, this macromonomer, and its derivatives, can be used as a performance-enhancing additive for a UV-curable adhesive.
In yet another aspect, the above-described macromonomer can be used in the preparation of water-dispersible polyurethanes. For this use, the macromonomer is co-polymerized with a monomer selected from the group consisting of acrylic acid, methacrylic acid, fumaric acid, maleic acid, and combinations thereof, in order to produce a co-polymer containing hydroxyl and acid moieties. At least a portion of the hydroxyl moieties on the copolymer are then reacted with an isocyanate to provide the water dispersible polyurethane.
These and other aspects of the present invention will become apparent upon reading the following detailed description of the invention.
It has now been surprisingly found that macromonomers produced in accordance with the present invention using a continuous addition of starter methodology are particularly useful in fabricating water-reducing additives for concrete-forming compositions, in producing dispersants for water-dispersible polyurethanes and performance enhancing additives for UV curable compositions. Illustratively, the macromonomers are reacted with a vinyl monomer to produce a co-polymer that is useful as a water-reducing additive (WRA) in concrete-forming compositions.
The macromonomers are prepared at a relatively low reaction temperature (between about 60 degrees and about 130 degrees Centigrade, preferably between about 60xc2x0 C. and about 110xc2x0 C.) in the presence of a relatively low concentration of a DMC catalyst (5 ppm to 500 ppm, preferably 5 ppm to 50 ppm), optionally in the presence of a solvent. The relatively low concentration of DMC catalyst, together with the relatively low reaction temperature, has been found by the present inventor to reduce or minimize the homopolymerization of the acrylate and methacrylate reactants. These reaction parameters have also been found to reduce or minimize the trans-esterification of hydroxyalkyl methacrylate and hydroxyalkylacrylate to form unwanted di-methacrylate and di-acrylate by-products. These byproducts are undesirable since they would be detrimental to the present inventor""s envisioned use of the macromonomers as intermediates in the production of dispersants for water-dispersed polyurethanes, as well as the other uses described herein.
The macromonomers produced in accordance with the present invention are made using CAOS methodology wherein the methacrylate or acrylate xe2x80x9cstarterxe2x80x9d is continuously added during the course of the reaction. The alkylene oxide compound employed in oxyalkylating the xe2x80x9cstarterxe2x80x9d or xe2x80x9cinitiatorxe2x80x9d may be any alkylene oxide polymerizable with DMC catalysts.
Suitably, the alkylene oxide is selected from the group consisting of ethylene oxide, propylene oxide, butylene oxide, and combinations thereof. Illustrative compounds include ethylene oxide, propylene oxide, 1,2- and 2,3-butylene oxide, C6-30 alpha-olefin oxides, glycidol, and halogenated alkylene oxides. Preferred are propylene oxide and ethylene oxide.
Mixtures of more than one alkylene oxide many be used, for example, mixtures of propylene oxide and ethylene oxide. Alkylene oxides, and their mixtures, may be polymerized onto the initiator molecules in one or more stages, to produce homopolymers, block copolymers, random copolymers, block random copolymers and the like. xe2x80x9cCopolymerxe2x80x9d in the present application includes xe2x80x9cterpolymerxe2x80x9d and mixtures of more than three alkylene oxides as well.
Other co-monomers may be polymerized along with the alkylene oxide. Examples of copolymerizable monomers include those disclosed in U.S. Pat. Nos. 3,278,457; 3,278,458; 3,404,109; 3,538,043; 3,900,518; 3,941,849; 4,472,560; 5,145,833; and 5,223,583 which are herein incorporated by reference. Glycidol is a particularly preferred copolymerizable monomer, and it may be used to introduce additional hydroxyl functionality.
Suitable DMC catalysts are well known to those skilled in the art. DMC catalysts are non-stoichiometric complexes of a low molecular weight organic complexing agent, and optionally other complexing agents, with a double metal cyanide salt, e.g. zinc hexacyanocobaltate. Exemplary DMC catalysts include those suitable for preparation of low unsaturation polyoxyalkalene polyether polyols, as disclosed in U.S. Pat. Nos. 3,427,256; 3,427,334; 3,427,335; 3,829,505; 4,472,560; 4,477,589; and 5,158,922. Preferably, however, the DMC catalysts used in accordance with the preferred aspects of the present invention are those capable of preparing xe2x80x9cultra-lowxe2x80x9d unsaturation polyether polyols such as polypropylene glycols and random EO/PO copolymers. The polyoxyalkylene polymers produced by the catalysts typically have levels of unsaturation (other than the purposefully introduced unsaturation of the subject invention starter molecules) less than about 0.010 meq/g, as measured by ASTM D-2849-69, xe2x80x9cTESTING OF URETHANE FOAM POLYOL RAW MATERIALSxe2x80x9d. Such catalysts are disclosed in U.S. Pat. Nos. 5,470,813 and 5,482,908, and 5,545,601, and these patents are incorporated herein by reference in their entirety. Preparation of the macromonomers of the present invention is facilitated using such highly active DMC catalysts.
Oxyalkylation conditions may be varied to suit the particular reactive unsaturation-containing initiator, alkylene oxide, and the like. For example, with liquid or low melting initiators, oxyalkylation may be effected by oxyalkylating neat, while with these same initiators or with solid initiators of higher melting point, oxyalkylation in solution or suspension in an inert organic solvent may be desired. Suitable solvents include aprotic polar solvents such as dimethylsulfoxide, dimethylacetamide, N-methyl-pyrrolidone, dimethylformamide, acetonitrile, methylene chloride, and especially the more volatile hydrocarbon solvents such as benzene, toluene, ethylbenzene, cyclohexane, petroleum ether, methylethylketone, cyclohexanone, diethylether, tetrahydrofuran, and the like.
It has been found that certain hard-to-dissolve initiators may be initially oxyalkylated in suspension in an organic liquid such as toluene, and following oxyalkylation with from 1 to 4 mols of alkylene oxide, will form soluble reaction products which can be further oxyalkylated in solution.
Oxyalkylation temperatures and pressures are conventional when employing vinyl polymerization inhibitors. Temperatures may range from room temperature or below to about 150xc2x0 C., or higher. Preferably, temperatures in the range of 70xc2x0 C. to 140xc2x0 C. are used, more preferably about 70xc2x0 C. to 110xc2x0 C. When highly active DMC catalysts capable of producing ultra-low unsaturation (less than 0.010 meq/g) are used, and the reaction is conducted at a low temperature, i.e. below 110xc2x0 C., and most preferably in the range of 70xc2x0 C. to 100xc2x0 C., then polyoxyalkylation can occur at reasonable rates without additional polymerization of the unsaturated moieties present. This is true even in the absence of a vinyl polymerization inhibitor. Alkylene oxide pressure is adjusted to maintain a suitable reaction rate, consistent with the ability of the process system to remove heat from the reactor. Pressures from 2 psia or lower to about 90 psia are useful. A pressure of 2 to 15 psia, 2 to 10 psia when employing propylene oxide, ethylene oxide, or a mixture of these alkylene oxides, may be advantageous.
Catalyst concentration is generally expressed as ppm based on the weight of the product. The amount of catalyst will depend upon the activity of the particular DMC catalyst. When using very active catalysts, such as those disclosed in U.S. Pat. Nos. 5,470,813; 5,482,908; and 5,545,601, amounts from less than 5 ppm to 500 ppm or higher are useful, more preferably from about 15 ppm to about 150 ppm.
In a typical synthetic procedure, the reaction is effected using a continuous addition of the initiator during the course of the reaction as disclosed in copending U.S. application Ser. No. 08/597,781, hereby incorporated by reference. For example, the initiator or initiators may be fed to the reactor continuously, either dissolved in alkylene oxide, dissolved in inert diluent, or, with liquid initiators, neat. The continuous addition of the initiator(s) may also be accompanied by continuous removal of product, resulting in a continuous synthesis process, as disclosed in U.S. application Ser. No. 08/683,356, also incorporated herein by reference.
The oxyalkylation of the reactive-unsaturation containing molecule is suitably conducted in the presence of a vinyl polymerization inhibitor, preferably of the type which function without the presence of oxygen, since oxyalkylations are generally xe2x80x9cin vacuoxe2x80x9d, meaning in this case that virtually the entire reactor pressure is due to alkylene oxide; or in the presence of a gas inert to the process, e.g. argon, nitrogen, etc. In other words, the partial pressure of oxygen, generally, is substantially zero. It is common to flush oxyalkylation reactors with nitrogen one or more times prior to final evacuation and introduction of alkylene oxide. Suitable inhibitors are well known to those skilled in the art of vinyl polymerization. Suitable inhibitors are, for example, butylated hydroxy toluene (BHT), 1,4-benzoquinone, 1,4-napthoquinone, diphenylphenylhydrazine, ferric chloride, copper chloride, sulfur, aniline, t-butyl-catechol, trinitrobenzene, nitrobenzene, 2,3,5,6-tetrachloro-1,4-benzoquinone (chloranil), and the like. BHT is preferred.
The inhibitor should be used in an amount effective to inhibit polymerization of the reactive unsaturation-containing inhibitor. Thus, the amount will vary with the reactivity of the particular type of unsaturation. Acrylates and methacrylates, for example may require higher levels of inhibitor than less reactive unsaturation-containing initiators. The amount of inhibitor will also vary with oxyalkylation temperature, with higher temperatures requiring higher amounts of inhibitor. Amounts of inhibitor, in weight percent relative to the weight of the reactive-unsaturation containing initiator, may vary from about 0.01 weight percent to about 1 weight percent, and more preferably from about 0.05 weight percent to about 0.5 weight percent. The latter range is particularly useful with BHT. If the vinyl polymerization inhibitor is not used, particularly with less active DMC catalysts, the product may be highly colored, or gelling of the product may occur.
Following oxyalkylation, the macromonomer may be vacuum stripped, for example using a stream of nitrogen, to remove unreacted monomers and other volatile components. The products may also be filtered to remove traces of DMC catalysts or their residues, or the products may be subjected to other methods of catalyst removal. When DMC catalysts of the ultra-low unsaturation-producing type are employed, the small amounts of catalysts used may be left in the product, or the product may be subjected to simple filtration to remove the catalysts and their residues.
The macromonomer is suitably reacted with a monomer such as acrylic acid, methacrylic acid, fumaric acid, styrene, maleic acid, methyl methacrylate, and combinations thereof, at a reaction temperature of between about 0xc2x0 C. and about 100xc2x0 C., preferably between about 30xc2x0 C. and about 60xc2x0 C., to prepare products useful in a variety of applications.
Illustratively, the macromonomer thusly produced may be used to prepare the dispersant for water reducing admixture for concrete, polymer polyol, or water-dispersed polyurethanes by reacting the intermediate with a vinyl monomer, such as acrylonitrile, styrene, acrylic acid, methacrylic acid, methylmethacrylate, methylacrylate, p-methylstyrene, or the like. A vinyl polymerization initiator, e.g. an organic peroxide, hydroperoxide, peroxyester, azo compound, ammonium persulfate, or the like, is optionally added, and polymerization commenced. Examples of suitable free radical polymerization initiators include acyl peroxides such as dihexanoyl peroxide and dilaurolyl peroxide, alkyl peroxides such as t-butyl peroxy-2-ethylhexanoate, t-butylperpivalate, t-amylperoctoate, 2,5-dimethyl-hexane-2,5-di-per-2-ethylhexoate, t-butyl-per-dodecanoate, t-butylperbenzoate and 1,1-dimethyl-3-hydroxybutylperoxy-2-ethylhexanoate, and azo catalysts such as azobis(isobutyronitrile), 2,2xe2x80x2-azo-bis-(2-methylbutyronitrile), and mixtures thereof. Ammonium persulfate and other water-soluble initiators are preferred. Redox initiator systems are also suitable for use in this invention.
The polymerization initiator concentration employed is not critical and can be varied considerably. As a representative range, the concentration can vary from about 0.1 to about 5.0 weight percent or even more, based upon the total feed to the reactor. Up to a certain point, increases in the catalyst concentration result in increased monomer conversion, but further increases do not substantially increase conversion. The particular catalyst concentration selected will usually be an optimum value considering all factors, including costs. It has been determined that low concentrations can be used in conjunction with high potency preferred stabilizers while still obtaining the desired dispersants for water reducing admixture for concrete, water-dispersed polyurethane, and polymer polyol.
In preparing water-dispersible polyurethanes, at least a portion of the hydroxyl moieties present on the co-polymer is suitably reacted with an isocyanate. Any isocyanate may be employed, such as an aromatic isocyanate, i.e. toluene diisocyanate (TDI), or an aliphatic isocyanate, such as hexamethylene diisocyanate (HDI), or combinations thereof. Other useful isocyanates include isophorone diisocyanate (IPDI), ethylene diisocyanate, 1,4-tetramethylene diisocyanate, 2,2,4-trimethyl-1,6-hexamethylene diisocyanate, 1,10-decanemethylene diisocyanate, 1,12-dodecanemethylene diisocyanate, cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate, 1-isocyanato-2-isocyanatomethyl cyclopentane, isophorone diisocyanate, bis-(4-isocyanatocyclohexyl)-methane, 1,3- and/or 1,4-bis-(isocyanatomethyl)-cyclohexane, bis-(4-isocyanato-3-methyl-cyclohexyl)-methane, 1-isocyanato-1-methyl-4(3)-isocyanatomethyl cyclohexane, 4,4xe2x80x2-dicyclohexylmethane diisocyanate, and combinations thereof.
As used herein, all percents are by weight unless otherwise specified, xe2x80x9cppmxe2x80x9d designates xe2x80x9cparts per millionxe2x80x9d, and all temperatures are in xe2x80x9cdegrees Centigradexe2x80x9d unless otherwise specified.
The following examples are intended to illustrate, but in no way limit the scope of, the present invention.